JP2013024809A - Surface inspection device and surface inspection method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately detect surface defects continuously existing in a longitudinal direction of a steel bar or the like.SOLUTION: A surface inspection device 15 of the present invention includes: illumination means 16 for illuminating a surface of long material 2 to be inspected; imaging means 17 for imaging the surface of the material 2 to be inspected; and image processing means 18 for processing the image imaged by the imaging means 17 and detecting a defect. Two illumination means 16 which form different included angles from and to the imaging means 17 are arranged around the material 2 to be inspected. When the illumination means 16 are turned on alternately and a defect is detected, one of the illumination means 16 is turned on according to a position of the defect and a defect is sequentially detected.

Description

  The present invention relates to a technique for inspecting defects on the surface of a long inspection object, and more particularly to a technique for inspecting defects with high accuracy without depending on the position and shape of the surface defects.

  Conventionally, wire rods, steel bars, steel pipes, and the like are generally manufactured by rolling a rolled material hot or cold. The rolling speed (passing speed) of the rolled material is, for example, 100 m / sec, which is very fast, and it is very difficult to find the surface flaws of the rolled material visually during passing. Therefore, in order to inspect defects (surface defects) of the rolled material while rolling, the occurrence of defects is automatically detected by various nondestructive inspection devices. As a method for inspecting the surface of a rolled material (inspected material), electromagnetic flaw detection such as eddy current flaw detection and leakage magnetic flux flaw detection is widely used. However, due to vibration of the inspection material and uneven electromagnetic characteristics of the inspection material. In many cases, error detection becomes a problem due to noise.

On the other hand, an optical automatic surface inspection apparatus using a high-speed camera has been developed in recent years.
In general, when optically inspecting circular cross-section inspected materials (wires, steel bars, steel pipes) that are manufactured continuously, the inspected material is illuminated using illumination means, except for self-luminous images that image high-temperature objects. It is necessary to irradiate light. As an illumination method, there is a case where a circular ring illumination that allows a material to be inspected to pass therethrough is used. Illumination is arranged on one or both sides of the upstream and downstream sides of the imaging system, and the material to be inspected is irradiated with illumination light incident slightly obliquely in the longitudinal direction. The light reflected by the inspection material and incident on the imaging optical system becomes an image of the inspection material. If the material to be inspected is defective, the reflection state of the illumination changes as compared with a normal part, so that it can be recognized as a dark part or a bright part on the image.

By the way, inspected materials include random wrinkles that occur irregularly and continuous wrinkles that occur continuously. Continuous dredging is very harmful, and if it does not occur early, it will be abolished and lead to a decrease in yield. As a surface inspection apparatus, it is necessary to detect not only random wrinkles but also continuous wrinkles with high accuracy.
As a conventional surface inspection apparatus, there is a surface flaw inspection apparatus disclosed in Japanese Unexamined Patent Publication No. 2009-8659 (Patent Document 1). This surface flaw inspection apparatus detects a surface flaw candidate of a material to be inspected by performing eddy current flaw detection or leakage magnetic flux flaw detection, and then images a predetermined area on the surface of the material to be inspected including the surface flaw candidate, and images the imaging results. The presence or absence of surface defects is determined by processing. In many cases, the flaw detection apparatus is used as a means for finding a surface flaw candidate because erroneous detection is often a problem due to vibration of a material to be inspected or noise generated due to uneven electromagnetic characteristics. Illumination used for the imaging means is arranged upstream and downstream in the conveyance direction of the material to be inspected to image the material to be inspected. When a surface flaw is present on the material to be inspected, the intensity of reflected light and scattered light from the light source changes compared to the normal part, so that it can be recognized as a dark part or a bright part on the image.

  As another surface inspection device, there is a surface flaw inspection device disclosed in JP 2009-507 211 (Patent Document 2). This surface flaw inspection apparatus detects a surface flaw of an inspection object such as a rolled / drawn metal bar. In this apparatus, a plurality of light sources are installed so as to cover 360 ° around the material to be inspected so that the surface luminance of the material to be inspected is substantially uniform, and a surface image is taken by a plurality of cameras. For dust prevention and packaging, a mirror is used in the optical system so that the angle formed by the optical path of the incident light from the light source to the material to be inspected and the optical path of the reflected light from the material to be inspected to the camera is about 1 °.

JP 2009-8659 A Special table 2009-507221 gazette

However, the techniques disclosed in Patent Document 1 and Patent Document 2 have the following problems.
Defects that continue in the longitudinal direction of the surface of the material to be inspected can be recognized as bright or dark because it depends on the positional relationship between the illumination angle of illumination and the surface defects and the shape of the surface defects. If illumination is installed in all 360 ° directions so that the luminance distribution in the circumferential direction is uniform, in addition to scattered light due to defects, there is usually also strong scattered light from the surface. The light is not emphasized and the defect cannot be detected accurately. That is, regardless of the position and shape of the surface defect, it is necessary to accurately detect the defect on the surface of the material to be inspected, but the defect cannot be detected as such.

  The present invention aims to provide a surface inspection apparatus and a surface inspection method capable of accurately detecting surface defects that are continuously present in the longitudinal direction of a steel material in order to solve the above-mentioned problems, and as a result, it is continuously manufactured. An object of the present invention is to provide a surface inspection apparatus and a surface inspection method that suppress mass disposal of steel materials and contribute to yield improvement.

In order to achieve the above-described object, the present invention takes the following measures.
The surface inspection apparatus of the present invention includes an illuminating means for illuminating the surface of a long inspection material, an imaging means for imaging the surface of the inspection material, and an image of the surface of the inspection material imaged by the imaging means. In the surface inspection apparatus including an image processing unit that detects defects by processing, the illumination unit illuminates the surface of the inspection material by changing an irradiation angle with respect to the inspection material.

Preferably, the illuminating unit includes a plurality of light sources having different irradiation angles on the inspection target viewed from the imaging unit, and illuminates the surface of the inspection target by switching the plurality of light sources.
Preferably, the surface inspection apparatus illuminates the surface of the inspection object by continuously switching on and off a plurality of light sources having different irradiation angles until a defect is detected by the image processing unit, When a defect is detected by the image processing means, a control means for controlling the illuminating means to illuminate the surface of the material to be inspected with a light source determined to be lit based on the position of the detected defect. It is good to have.

  Preferably, the surface inspection apparatus detects a defect while the material to be inspected is in progress, and the plurality of illumination devices include a first illumination device and a second illumination device, and the illumination device and the imaging unit Is arranged on a surface that intersects in a direction perpendicular to the traveling direction of the material to be inspected, and the first illumination device has an angle between 0 to 45 ° with the imaging means, and the second illumination device. The illumination device may have a sandwich angle of 45 to 90 ° with the imaging unit.

  Preferably, the surface inspection apparatus illuminates the surface of the inspection object by alternately turning on the first illumination apparatus and the second illumination apparatus until a defect is detected by the image processing means. When a defect is detected, the surface of the material to be inspected is illuminated by one of the first illumination device and the second illumination device that are determined to be lit based on the position of the detected defect. Thus, it is preferable to provide a control means for controlling the illumination means.

Preferably, the control means turns on the second illumination device when the position of the detected defect is in the center of the field of view of the imaging means, and the position of the detected defect is the end of the field of view. In such a case, the lighting means may be controlled so as to turn on the first lighting device.
Preferably, the illumination device and the imaging unit are arranged symmetrically on the surface.

Preferably, the illuminating unit may adjust the light amount so that the image luminance of the material to be inspected when captured by the imaging unit is sufficient.
Preferably, the illuminating unit adjusts the light amount so that the image luminance of the inspection object when imaged by the imaging unit is symmetric.
On the other hand, the surface inspection method of the present invention illuminates the surface of a long inspected material, images the surface of the inspected material, and processes the captured image of the surface of the inspected material to detect defects. In the surface inspection method, the surface of the inspection material is illuminated by changing an irradiation angle with respect to the inspection material.

  Preferably, the surface of the material to be inspected by the first illuminating device having an angle of 0 to 45 ° with the imaging means for imaging the surface of the material to be inspected and the second illuminating device having an angle of 45 to 90 °. Until the defect is detected, the first illumination device and the second illumination device are alternately turned on to illuminate the surface of the material to be inspected, and the defect is detected. The surface of the material to be inspected may be illuminated by one of the first illumination device and the second illumination device determined to be lit based on the position of the defect.

  ADVANTAGE OF THE INVENTION According to this invention, the surface defect which exists continuously in the longitudinal direction of steel materials can be detected with a sufficient precision, As a result, mass disposal of the steel materials manufactured continuously can be suppressed and it can contribute to a yield improvement.

It is a schematic diagram of rolling equipment. It is a conceptual diagram of a surface inspection apparatus. It is the layout (the 1) of the illumination and camera in a surface inspection apparatus. It is the layout (the 2) of the illumination in a surface inspection apparatus, and a camera. It is the layout (the 3) of the illumination and camera in a surface inspection apparatus. It is a flowchart which shows the procedure of a defect detection determination process. It is a flowchart which shows the procedure of a defect tracking process. It is a figure explaining switching of outside illumination and inside illumination. It is an image when the surface of a to-be-inspected material is imaged. It is a change figure of the brightness when the surface flaw is imaged. It is a change figure of a luminance differential absolute value when a surface flaw is imaged.

Hereinafter, a surface inspection apparatus and a surface inspection method according to an embodiment of the present invention will be described. In the following description, the same parts are denoted by the same reference numerals. Their names and functions are also the same. Therefore, detailed description thereof will not be repeated.
The surface inspection apparatus and the surface inspection method according to the present embodiment are for inspecting the surface defects of a long material to be inspected, for example, for inspecting the surface defects of a wire, a steel bar, and a steel pipe. A description will be given by taking a wire as an example. FIG. 1 shows a rolling facility for producing a wire rod.

The rolling equipment 1 is, for example, for continuously rolling a rolled material 2 made of a steel material to produce a wire, and a heating furnace 3, a descaler 4, and rough rolling for heating the rolled material 2 from the upstream side toward the downstream side. The machine 5, the intermediate rolling mill 6, the finish rolling mill 7, and the winding machine 8 are arranged in order. In addition, the rolling equipment 1 of FIG. 1 may manufacture a bar steel and a steel pipe by rolling the rolling material 2 continuously.
In the following description, the left side of FIG. 1 is the upstream side, and the right side of FIG. 1 is the downstream side.

  The heating furnace 3 is an apparatus for heating the rolled material 2 to about 1000 to 1200 ° C., and the rolled material 2 heated in the heating furnace 3 is sent to the descaler 4. The descaler 4 is a device that removes the subscale formed on the surface of the rolled material 2 after heating with the action of water vapor, spraying high-pressure washing water, or a mechanical brush. The material 2 is sent to the roughing mill 5. The rough rolling mill 5, the intermediate rolling mill 6 and the finish rolling mill 7 roll the rolled material 2 to a predetermined size, and the rolled material 2 rolled to a predetermined size by the finishing rolling mill 7 is a winder. The rolled material 2 is wound up in a ring shape.

The rough rolling mill 5, the intermediate rolling mill 6, and the finish rolling mill 7 are provided with a plurality of rolling stands 10 having a pair of rolling rolls 9, 9. The rolling roll 9 is formed in a cylindrical shape or a columnar shape, and various shapes of calibers 11 are formed on the outer peripheral surface (outer peripheral portion) thereof. On each rolling stand 10, rolling rolls 9 are arranged in various directions.
According to this rolling equipment 1, the rolled material 2 is passed through each rolling stand 10, and the rolling roll 9 is rolled with respect to the rolled material 2 from various angles such as a horizontal direction and a vertical direction. The rolled material 2 can be rolled to a predetermined size by sequentially reducing the cross section of the rolled material 2 while deforming it into corners, ellipses, circles, and the like.

  Now, when the rolling material 2 is rolled with such a rolling roll 9, a long wrinkle may enter the surface of the rolling material 2 in the longitudinal direction. If wrinkles (surface wrinkles) enter the surface of the rolled material 2, the portion containing the surface wrinkles must be discarded. Don't be. According to the present invention, the surface defect of the rolled material 2 can be quickly detected by the surface inspection device 15 and the surface inspection method.

The surface inspection device 15 is disposed on the downstream side of the finish rolling mill 7. The surface inspection device 15 may be provided between the rough rolling mill 5 and the intermediate rolling mill 6 and between the intermediate rolling mill 6 and the finish rolling mill 7. Hereinafter, the surface inspection apparatus 15 and the surface inspection method will be described in detail.
FIG. 2 is a conceptual diagram of the surface inspection apparatus 15. As shown in FIG. 2, the surface inspection apparatus 15 includes an illumination unit 16, an imaging unit 17, and an image processing unit 18.

  The illuminating means 16 illuminates the surface of the long inspected material (rolled material) 2 and is composed of, for example, an LED illumination unit, and at least a predetermined interval around the inspected material 2 Two are arranged. More specifically, the illumination unit 16 is arranged around the material to be inspected 2 so that the sandwiching angle with the imaging unit 17 is a predetermined angle. The imaging means 17 is for imaging the surface of the material to be inspected 2 and is composed of a line camera or area camera using a CCD or CMOS, and at least around the material to be inspected 2 like the illumination means 16. One is arranged. The image processing means 18 detects the defect by processing the image of the surface of the inspection object 2 imaged by the imaging means 17 and is constituted by a computer or the like.

  FIG. 3 is a layout diagram of the illumination means (illumination device) 16 and the imaging means (camera) 17. In FIG. 3, the material 2 to be inspected advances from the back to the front or from the front to the back. The illuminating device (1) 16 in FIG. 3 is installed so that the sandwiching angle θ (1) with the camera 17 is 0 to 45 °, and irradiates the defect (1) of the inspected material 2 from an oblique direction. It is suitable for detecting scattered light. However, in the illumination device (1) 16, the scattered light from the defect (2) is also affected by the reflected light from the surface in the vicinity of the defect (2), so that the defect (2) cannot be emphasized and detected. .

  On the other hand, the illumination device (2) 16 is installed so that the sandwiching angle θ (2) with the camera 17 is 45 to 90 °, and irradiates the defect (2) of the inspection object 2 from an oblique direction. It is suitable for detecting scattered light from a defective surface. However, in the illumination device (2) 16, the scattered light from the defect (1) is also affected by the reflected light from the surface in the vicinity of the defect (1), so that the defect (1) cannot be emphasized and detected. .

In consideration of this, for detecting defects in the inspection object 2 existing continuously in the longitudinal direction, the illumination device (1) and the illumination device (2) are placed one by one for a predetermined time (for example, 0.5 seconds). ) Is effective because both the defect (1) and the defect (2) shown in FIG. 3 can be accurately detected.
Further, FIG. 4 shows a diagram in which two lighting devices 16 are added to the configuration of FIG. In FIG. 4, the illumination device (3) 16 is installed at the illumination device (1) 16 and the illumination device (4) 16 is installed at the left and right inverted positions (angles). Enable detection. Further, it is possible to detect the defect (3) that cannot be detected or difficult to detect with the configuration of FIG. As shown in FIG. 4, by arranging the illumination device 16, it is possible to detect a defect in the circumferential direction 90 ° range of the inspection object 2.

  Further, FIG. 5 is an example of a layout diagram of the camera 17 and the illumination device 16 that can detect a 360 ° defect around the material 2 to be inspected. The sandwich angle between the camera (1) 17 and the illumination device (1) 16 is θ (1), the sandwich angle between the camera (1) 17 and the illumination device (2) 16 is θ (2), and the camera (4) 17 and the illumination. The camera (1) 17, the illuminating device (1) 16, the illuminating device (2) 16 and the camera (4) 17 are arranged so that the sandwiching angle of the device (2) 16 is θ (1). As shown in FIG. 5, with the same angular arrangement, as shown in FIG. 5, the lighting device (4) 16, the lighting device (5) 16, the lighting device (6) 16, the lighting device (7) 16, and the lighting device (8) The camera 16, the camera (2) 17, and the camera (3) 17 are installed.

  Arranging in this way, the lighting device 16 is switched on / off. First, as shown in FIG. 5A, the lighting device (1) 16, the lighting device (3) 16, the lighting device (5) 16, and the lighting device (7) 16 are turned off, and the lighting device (2) 16, By illuminating the illumination device (4) 16, the illumination device (6) 16 and the illumination device (8) 16, the camera (1) 17 and the camera (3) 17 detect a defect existing near the center of the visual field. The camera (2) 17 and the camera (4) 17 detect defects existing near the edge of the field of view.

  Further, as shown in FIG. 5B, the lighting device (1) 16, the lighting device (3) 16, the lighting device (5) 16, and the lighting device (7) 16 are turned on, and the lighting device (2) 16, By turning off the illuminating device (4) 16, the illuminating device (6) 16 and the illuminating device (8) 16, the camera (1) 17 and the camera (3) 17 detect defects near the edge of the field of view, A camera (2) 17 and a camera (4) 17 detect a defect existing near the center of the field of view.

In this way, by switching on / off the lighting device 16, a 360 ° defect around the material to be inspected 2 can be detected. When attention is paid only to the lighting device (1) 16, the lighting device (1) 16 functions as a lighting device with respect to both the camera (1) 17 and the camera (4) 17, so that There is an effect that the number can be reduced.
2-5, the illuminating device 16 and the camera 17 are arrange | positioned on the surface which cross | intersects the orthogonal | vertical direction with respect to the advancing direction of the to-be-inspected material 2. As shown in FIG. This vertical direction does not need to be completely vertical (90 °), and does not need to be located on the same plane. The illumination device 16 having different irradiation angles may be switched, and any arrangement may be used as long as the bright portion or the dark portion appears in the captured image based on the shape and position of the defect on the surface of the inspection object 2.

Next, the procedure of defect detection determination processing executed by the image processing means (computer) 18 will be described with reference to FIG.
In the flowchart of FIG. 6, a defect is detected from the average luminance of n frames. For example, when the imaging rate is 10,000 lines / second and determination is made every 0.05 seconds, the constant n is 500.

In step 1 (hereinafter, “step” is described as “S”), 1 is substituted for variable a, and in S2, variable a is substituted for variable i. In S3, it is determined whether variable i is (a + n-1). If so (Yes in S3), the process proceeds to S5. If not (No in S3), the process is performed. Moved to S4.
In S4, 1 is added to the variable i. Thereafter, the process returns to S3. In S5, the differential absolute value of the luminance average of a to (a + n-1) frames is calculated. At this time, the number of frames for which the luminance average is calculated is n.

In S6, it is determined whether or not the differential absolute value calculated in S5 exceeds the threshold value. If so (Yes in S5), the process proceeds to S7. If not (No in S5). ) The process proceeds to S8.
If it is determined that a defect exists (S7), the process proceeds to S8. In S8, it is determined whether or not the variable a exceeds the length of the material 2 to be inspected. If so (Yes in S8), the process ends. If not (No in S8), the process ends. Is moved to S9. In S9, n is added to the variable a. Thereafter, the process returns to S2.

  In the defect detection determination method shown in FIG. 6, the absolute value obtained by differentiating the average luminance value in consecutive n frames (500 frames in the above description) may exceed a preset threshold value. It is determined that there is a defect. In addition to the luminance differential absolute value, the presence or absence of a defect may be determined by detecting a high-frequency component by applying a high-pass filter. Such a process is repeatedly performed until the length of the inspection target of the inspection target material 2 is exceeded.

  In this way, when it is determined that there is a defect, the surface inspection apparatus 15 according to the present embodiment switches the illumination as follows so that the detected defect can be followed and detected. For the outer lighting device 16 and the inner lighting device 16 that have been switched on / off at 0.5 second intervals until it is determined that a defect exists, only one of them is turned on if it is determined that a defect exists. Switch the other to turn off.

The procedure of such defect following processing (illumination control processing) will be described with reference to FIG. Note that the control for turning on and off the lighting device 16 is performed by the image processing means (computer) 18 described above. The control of the illumination device 16 is not limited to this, and other control devices may be used.
In S11, it is determined whether or not there is a passage signal of the material to be inspected 2 from the upper process. If it is determined that there is a passage signal (Yes in S11), the process is moved to S12. (No in S11) The process returns to S11 and waits for a passing signal. If there is a passing signal of the inspection object 2 from the upper process, it indicates that the inspection object 2 will arrive at the surface inspection apparatus 15 soon.

  In S12, switching of lighting device 16 (repetition of turning on and off) is started. At this time, the outer illumination device 16 (illumination device (2) 16 and illumination device (4) 16 shown in FIG. 4), and the inner illumination device 16 (illumination device (1) 16 and illumination device (3) shown in FIG. 4). ) 16) is turned on / off at intervals of 0.5 seconds. The lighting device (2) 16 and the lighting device (4) 16 are turned on / off at the same timing, and the lighting device (1) 16 and the lighting device (3) 16 are turned on / off at the same timing.

  In S13, the defect detection process is started. In S14, it is determined whether or not a defect exists in the inspection object 2. The details of the determination process are as shown in FIG. If there is a defect in the inspection object 2 (Yes in S13), the process is moved to S16. If not (No in S13), the process is moved to S15, and the lighting device 16 is switched (repetition of turning on and off). Be started. Thereafter, the process returns to S13 to continue detecting defects. In S15, when switching of lighting device 16 (repetition of lighting / extinguishing) has already been started, switching (repetition of lighting / extinguishing) is continued.

  In S16, the maximum position x of the defect is searched. The position x searched at this time is calculated as 0 <x <w, where w is the width of the inspection object 2 in the image. In S17, it is determined whether or not the searched defect maximum position x satisfies 0.35w <defect maximum position x <0.65w. If 0.35w <defect maximum position x <0.65w (Yes in S17), the process proceeds to S18. If not (No in S17), the process proceeds to S19.

In S18, the outer lighting device 16 is turned on and the inner lighting device 16 is turned off. In S19, the outer lighting device 16 is turned off and the inner lighting device 16 is turned on. After the processes of S18 and S19, the process is moved to S20.
In S20, it is determined whether or not there is a passing signal of the inspection material 2, and if the inspection material 2 passes through the surface inspection device 15 (Yes in S20), the process is returned to S13 and the defect is detected. If the detection is continued and the inspection object 2 has not passed through the surface inspection device 15 (No in S20), the process is terminated.

A surface inspection method using the surface inspection apparatus 15 having the above-described structure and flowchart will be described. In the description of the surface inspection method, it is assumed that four illumination devices 16 are mainly arranged as shown in FIG.
When the material 2 to be inspected flows from the upper process to the surface inspection device 15 (Yes in S11), the outer illumination device 16 (illumination device (2) 16 and illumination device (4) 16 in FIG. 4) and the inner illumination device 16 Turning on / off the illumination device 16 (illumination device (1) 16 and illumination device (3) 16 in FIG. 4) is switched every 0.5 seconds. At this time, focusing only on a specific 0.5 second, the outer two illumination devices 16 (illumination device (2) 16 and illumination device (4) 16) and the inner two illumination devices 16 (illumination devices ( 1) Only two lighting devices 16 on one side of 16 and lighting device (3) 16) are turned on (S12).

  As long as the defect detection is started (S13) and the inspected material 2 passes the surface inspection apparatus 15 (until determined to be Yes in S8), whether or not there is a defect in the processes of S1 to S7. Is determined. If it is determined that a defect exists (Yes in S6, Yes in S7, S14), the maximum defect position x is searched (S16). When the searched defect maximum position x satisfies 0.35w <x <0.65w (Yes in S17), the outer illumination device 16 is turned on and the inner illumination device 16 is turned off. If the maximum defect position x does not satisfy 0.35w <x <0.65w (No in S17), the outer lighting device 16 is turned off and the inner lighting device 16 is turned on. Thus, once a defect is detected on the surface of the inspection object 2, the inner lighting device 16 and the outer lighting device 16 that have been turned on and off at intervals of 0.5 seconds follow the detected defect. Thus, only one of the inner lighting device 16 and the outer lighting device 16 is turned on.

  When the lighting state of the lighting device is switched in this way, 0 to 0.35 w (pixel) or 0.65 w (pixel) to w (w) when the width of the inspection object 2 in the image is w (pixel). When the maximum defect exists in (pixel), the inner illumination device 16 is turned on (the outer illumination device 16 is turned off), and when the largest defect exists in 0.35w (pixel) to 0.65w (pixel) The outer lighting device 16 is turned on (the inner lighting device 16 is turned off). For example, as shown in FIG. 8, when the defect exists in 0.35w to 0.65w, the outer illumination device (2) 16 and the illumination device (4) 16 are turned on to accurately detect the defect near the center. Detect well. When a defect exists other than 0.35w to 0.65w, the inner illumination device (1) 16 and the illumination device (3) 16 are turned on to detect the defect near the end with high accuracy.

  FIG. 9 shows an image captured by the camera 17. As shown in FIG. 9, the defect (4) and the defect (5) are present on the surface of the inspection object 2. An image 9A shown on the lower side of FIG. 9 is an image obtained by lighting the inner lighting device (1) 16 and the lighting device (3) 16, and an image 9B shown on the upper side of FIG. It is the image imaged with the device (2) 16 and the lighting device (4) 16 turned on.

  As shown in the lower image 9A in FIG. 9, when the inner lighting device 16 is turned on and the outer lighting device 16 is turned off, the defect (5) is not clearly imaged. On the other hand, as shown in the upper image 9B of FIG. 9, when the outer lighting device 16 is turned on and the inner lighting device 16 is turned off, the defect (4) and the defect (5) are imaged. This is because the outer illumination device 16 is installed so that the sandwiching angle θ (1) with the camera 17 is 45 to 90 °, and the defect (4) and the defect ( 5) shows that it is suitable for detecting scattered light from the defect surface. On the other hand, in the inner illumination device 16, the scattered light from the defect (4) and the defect (5) existing in the vicinity of the central portion of the inspection object 2 is also affected by the reflected light from the surface near the defect. Therefore, it is shown that the defect cannot be emphasized and detected.

FIG. 10 shows the luminance distribution obtained by processing the captured image shown in FIG. 9, and FIG. 11 shows the distribution of the luminance differential absolute value.
The luminance distribution 10A and the luminance differential distribution 11A correspond to the image 9A in which only the inner lighting device 16 is turned on, and the luminance distribution 10B and the luminance differential distribution 11B correspond to the image 9B in which only the outer lighting device 16 is turned on.

  When only the inner lighting device 16 is turned on, the defect (5) cannot be clearly detected as shown in the luminance distribution 10A, and the defect (5) can be detected with the threshold value as shown in the luminance differential distribution 11A. Absent. On the other hand, when only the outer illumination device 16 is turned on, the defect (4) and the defect (5) can be clearly detected as shown in the luminance distribution 10B, and the threshold (30) as shown in the luminance differential distribution 11B. The defect (4) and the defect (5) can be detected with the brightness differential absolute value of the degree.

  Further, a case where a plurality of defects are detected will be described. As shown in the image 9B (outer illumination device (2) 16 and illumination device (4) 16 are turned on), the defect (4) and defect (5) are detected. The defect maximum position x searched in S16 is near 160 pixels where the differential absolute value of luminance is maximum. Since the vicinity of 160 pixels exists between 0.35 w and 0.65 w, the outer lighting device 16 and the inner lighting device 16 that have been switched on and off are turned on. It shifts to the state where the inner illumination device 16 is turned off (S18). Thus, which lighting device 16 is to be turned on is determined by the maximum position x of the detected defect.

  Here, when the lighting device 16 and the camera 17 are arranged as shown in FIG. 5, a plurality of cameras 17 are arranged. For this reason, it is possible that one defect is imaged by two cameras 17 and a plurality of defects are imaged at the same timing. In such a case, the defect is detected with high accuracy by following the defect having the maximum evaluation value (for example, the above-described absolute value of the differential luminance).

  Further, as shown in the luminance distribution 10B, when the luminance distribution when the lighting device (2) 16 and the lighting device (4) 16 are turned on is viewed, the maximum value in the left half is the maximum value in the right half. Is less than half. In such a case, it is more preferable that there is a light amount adjustment function when the outer illumination device 16 during illumination switching in the flowchart of FIG. Specifically, when a defect is detected based on the luminance distribution of one image frame or a plurality of frames, if the maximum luminance of the left half of the inspection object 2 is 128 or less (half of 256 gradations to be saturated), the current luminance If k, the light source light amount of the illumination device 16 is adjusted to 128 / k times. Thereby, since image processing can be performed based on image data with sufficient luminance, defect detection can be performed with high accuracy. In addition, if the left half light source light amount is adjusted so as to be symmetric with the maximum luminance of the right half of the material to be inspected 2, image processing can be performed based on left-right symmetric image data, so that accurate defect detection is possible. become. In addition to this, it is possible to detect a defect with higher accuracy by adjusting the light source light amount so that the luminance is sufficient as described above.

As described above, the surface inspection apparatus according to this embodiment can accurately detect surface defects that exist continuously in the longitudinal direction of the material to be inspected. As a result, mass disposal of continuously manufactured steel materials can be suppressed, and the yield can be improved.
In particular, the surface inspection apparatus according to this embodiment has the following effects.
By switching illumination devices having different irradiation angles with respect to the material to be inspected, it is possible to detect a wide range of defects by highlighting bright or dark portions in the captured image based on the shape and position of the defects on the surface.

  Furthermore, the illumination is switched continuously until a surface defect is detected, and when detected, the defect is reliably confirmed by selecting and lighting the illumination that is obliquely irradiated to the defect according to the position of the detected defect. It can be detected following the above. Furthermore, in this case, even if a plurality of defects are detected, the illumination is selected following the defect that can obtain the maximum signal of the luminance differential absolute value, so that the defect is reliably followed and detected. Can do.

  Furthermore, since the lighting device is arranged and switched between a position where the angle between the camera and the camera is 0 to 45 ° and a position where it is 45 to 90 °, defects that cannot be detected by one lighting device can be detected by the other lighting. It is possible to compensate, and the defect can be reliably detected. Further, even when the number of cameras is increased and the entire surface of the material to be inspected is imaged with the camera, the lighting device can be configured with a plurality of cameras by arranging the units composed of the camera and the lighting device symmetrically. Can also be used. Furthermore, since it has a function of adjusting the light quantity of the illumination device, it is possible to detect a defect reliably even when the illumination device is switched.

The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.
For example, in the above-described embodiment, at least two illumination devices are arranged, but the illumination angle can be switched even with a single illumination device or a single light source incorporating two or more light sources having different illumination angles. It may be a single lighting device provided with a mechanism that can be used.

1 Rolling equipment 2 Rolled material (inspected material)
DESCRIPTION OF SYMBOLS 3 Heating furnace 4 Descaler 5 Coarse rolling mill 6 Intermediate rolling mill 7 Rolling mill 8 Winding machine 9 Roll roll 10 Rolling stand 11 Caliber 15 Surface inspection apparatus 16 Illumination means (illumination apparatus)
17 Imaging means (camera)
18 Image processing means

Claims (11)

An illuminating means for illuminating the surface of a long inspection material, an imaging means for imaging the surface of the inspection material, and an image for detecting defects by processing an image of the surface of the inspection material imaged by the imaging means In a surface inspection apparatus comprising a processing means,
The surface inspection apparatus characterized in that the illuminating means illuminates the surface of the inspection object by changing an irradiation angle to the inspection object.   The illumination unit includes a plurality of light sources having different irradiation angles to the inspection object viewed from the imaging unit, and switches the plurality of light sources to illuminate the surface of the inspection object. The surface inspection apparatus according to 1.   The surface inspection apparatus illuminates the surface of the material to be inspected by continuously switching on and off a plurality of light sources having different irradiation angles until a defect is detected by the image processing unit. And a control means for controlling the illuminating means to illuminate the surface of the material to be inspected with a light source determined to be lit based on the position of the detected defect. The surface inspection apparatus according to claim 2. The surface inspection apparatus detects defects during the progress of the inspection object,
The plurality of lighting devices include a first lighting device and a second lighting device,
The illuminating device and the imaging means are arranged on a surface that intersects in a direction perpendicular to the traveling direction of the material to be inspected, and the first illuminating device has an angle between 0 to 45 ° with the imaging means. The surface inspection apparatus according to claim 1, wherein the second illumination device has a sandwich angle of 45 to 90 ° with the imaging unit.   The surface inspection device illuminates the surface of the material to be inspected by alternately turning on the first illumination device and the second illumination device until a defect is detected by the image processing means. When detected, so as to illuminate the surface of the material to be inspected by one of the first illumination device and the second illumination device determined to be lit based on the position of the detected defect. The surface inspection apparatus according to claim 4, further comprising a control unit that controls the illumination unit.   The control means turns on the second illumination device when the position of the detected defect is in the center of the field of view of the imaging means, and the position of the detected defect is at the end of the field of view. The surface inspection apparatus according to claim 5, wherein the illuminating unit is controlled to turn on the first illuminating apparatus.   The surface inspection apparatus according to claim 4, wherein the illumination device and the imaging unit are arranged symmetrically on the surface.   8. The surface inspection according to claim 1, wherein the illumination unit adjusts a light amount so that an image luminance of a material to be inspected when captured by the imaging unit is sufficient. apparatus.   The surface inspection according to any one of claims 1 to 8, wherein the illuminating unit adjusts the amount of light so that an image luminance of a material to be inspected when imaged by the imaging unit is symmetric. apparatus. In the surface inspection method for detecting defects by illuminating the surface of a long inspection material, imaging the surface of the inspection material, processing the image of the surface of the imaged inspection material,
A surface inspection method for illuminating the surface of the material to be inspected by changing an irradiation angle to the material to be inspected. The surface of the material to be inspected is illuminated by the first illumination device having an angle of 0 to 45 ° with the imaging means for imaging the surface of the material to be inspected and the second illumination device having an angle of 45 to 90 °. ,
Until the defect is detected, the first illumination device and the second illumination device are alternately turned on to illuminate the surface of the inspection object. When the defect is detected, the position of the detected defect is detected. The surface inspection method according to claim 10, wherein the surface of the material to be inspected is illuminated by any one of the first illumination device and the second illumination device that are determined to be turned on. .